The world’s 49 most climate vulnerable countries have called on the G20 to finally set a date – preferably 2020 – for a phase out of fossil fuel subsidies.

The richest 20 nations have pledged to phase out “inefficient” fossil fuel subsidies over the “medium term”. But campaigners and investors have urged them to follow the G7 and set a deadline.

Those calls were repeated on Sunday by the finance ministers of the Climate Vulnerable Forum (CVF), a political grouping of the countries that are the most vulnerable to the effects of climate change because of geography and poverty.

In a communiqué issued at the end of its weekend meeting in Washington DC, the group called “for market distorting fossil fuel production subsidies to be removed immediately and no later than 2020, and urge the G20 to set such as adopt a clear timeframe for fossil fuel subsidy elimination”.

The CVF meeting, which was chaired by Ethiopia, said subsidies for fossil fuels could only be justified when they provided real benefits to the poor.

The G20, which represent the world’s largest economies, still pours hundreds of billions of dollars into the fossil fuel industry each year through tax breaks, direct finance and other forms of support. Definitions of what constitutes a subsidy are hotly contended, but the OECD has issued an estimate – which is considered conservative – that its member states give the industry support worth $160-200bn each year.

In a side meeting, representatives of the G20 met with the CVF, where the importance of a fossil fuel subsidy phase out was expressed.

G20 heads of state will meet in Hamburg in July. The German presidency is expected to prioritise climate change at the meeting, despite expected recalcitrance on the subject from Donald Trump’s new US administration.

The Paris climate agreement, struck in 2015, commits countries to limit global warming to “well below” 2C and pursue efforts “to limit the temperature increase to 1.5C”. As the most vulnerable countries, the CVF have the most immediate interest in keeping global temperatures below the latter, lower goal.

Macaya Hayes, ambassador of Costa Rica to the US, said: “For vulnerable countries, the 1.5C limit is a matter of survival. It requires immediate and swift action by the global community, and above all, the major industrial powers.”

Also occupying the minds of the most vulnerable countries is a promise of $100bn of finance that rich countries have promised to deliver each year to the poor world by 2020 to help them cope with climate change.

In a thinly-veiled reference the US government’s budget proposal to cease climate finance flows, the CVF communiqué said: “Pulling resources from climate protection will create economic instability. Investing in climate action is necessary and critical to inclusive development and economic growth”.

The meeting of the CVF also welcomed new members, with Colombia, Lebanon, the Gambia, Palestine and Samoa joining the forum. The Marshall Islands was elected to take over as chair from Ethiopia in 2018.